Spike, he has vampire strength and fighting skills. Giles is good, but not as strong, and Xander is useless. Willow is powerful with her magic, and Anya would be good as a venegenance demon but she's not good human. And Dawn, at the end, is just slightly more useful than Xander.

If we're talking physical fighting.. no contest.

Isn't this a little obvious?

you could argue spike isn't one of the scoobies though
out of the other i would say physical fight, giles
any kind, willow, although i guess willow could just give herself badass strength and skills

i dont think there was much of a contest there!

no doubt its Spike. Even buffy said that he is the stronger fighter they have.

i hate to say it, as a angel fan, but he is a good fighter. is this pick with or without the chip?

2 slayers he killed

Spike is a good fighter.

Buffy said so herself, after her, he's the only one strong enough!

I assume this was physically. Willow would have a chance if she used the end of season 6 spell for physical power but it would still be Spike he's had a lot more practice. ;)